使用Servlet对Mysql数据库表中数据进行增删改查
一： 要对数据库内的数据进行增删改查，首先我们需要连接到数据库
1）为了方便我们可以把jdbc代码写到一个Utils工具类内
package westos;
import java.sql.*;
public class Utils {
//这里的b是指你要查询的表名
static final String URL = "jdbc:mysql://localhost:3306/b?serverTimezone=GMT%2B8&useSSL=false" +
"&useServerPrepStmts=true&cachePrepStmts=true&rewriteBatchedStatements=true" +
"&useCursorFetch=true&defaultFetchSize=100&allowPublicKeyRetrieval=true";
//数据库用户名
static final String USERNAME = "root";
//数据库密码
static final String PASSWORD = "itcast";
static {
try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
public static Connection getConnection() throws SQLException {
Connection conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);
return conn;
}
public static void close(ResultSet rs, PreparedStatement stmt, Connection conn) {
if (rs != null) {
try {
rs.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (stmt != null) {
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
if (conn != null) {
try {
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
public static void close(PreparedStatement stmt, Connection conn) {
close(null, stmt, conn);
}
}
二：写好工具类后就可以写增删改查的代码了
增
@WebServlet(urlPatterns = "/insert")
public class Insert extends HttpServlet{
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
//req.getRequestDispatcher("login.jsp").forward(req,resp);
// 获取部门编号
String deptno = req.getParameter("deptno");
int no = Integer.parseInt(deptno);
// 获取部门名称
String dname = req.getParameter("dname");
// 获取地区
String loc = req.getParameter("loc");
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = Utils.getConnection();
stmt = conn.prepareStatement(
"insert into dept(deptno,dname,loc) values(?,?,?)");
stmt.setInt(1, no);
stmt.setString(2, dname);
stmt.setString(3, loc);
stmt.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
Utils.close(stmt, conn);
}
resp.sendRedirect("/select");
}
}
删
@WebServlet(urlPatterns = "/delete")
public class Delete extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String[] deptnos = req.getParameterValues("deptno");
Connection conn = null;
PreparedStatement stmt = null;
try{
conn = Utils.getConnection();
stmt = conn.prepareStatement("delete from dept where deptno=?");
for (String deptno : deptnos) {
int no = Integer.parseInt(deptno);
stmt.setInt(1, no);
stmt.executeUpdate();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
Utils.close(stmt, conn);
}
resp.sendRedirect("/select");
}
}
改
修改之前需要查询到原数据，才能便于修改（同时需要一个Dept实体类，将查询到的数据存放至作用域中）
@WebServlet(urlPatterns = "/update1")
public class Update1 extends HttpServlet{
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String deptno = req.getParameter("deptno");
int no = Integer.parseInt(deptno);
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = Utils.getConnection();
stmt = conn.prepareStatement("select deptno,dname,loc from dept where deptno=?");
stmt.setInt(1, no);
rs = stmt.executeQuery();
if(rs.next()) {
System.out.println(rs.getInt("deptno"));
System.out.println(rs.getString("dname"));
Dept dept = new Dept(
rs.getInt("deptno"),
rs.getString("dname"),
rs.getString("loc")
);
req.setAttribute("d", dept);
} else {
req.setAttribute("d", null);
}
req.getRequestDispatcher("update.jsp").forward(req,resp);
}catch (Exception e) {
e.printStackTrace();
} finally {
Utils.close(rs, stmt, conn);
}
}
}
Dept实体类
public class Dept {
private int deptno;
private String dname;
private String loc;
private boolean close;
public boolean isClose() {
return close;
}
public void setClose(boolean close) {
this.close = close;
}
public Dept(int deptno, String dname, String loc) {
this.deptno = deptno;
this.dname = dname;
this.loc = loc;
}
public int getDeptno() {
return deptno;
}
public void setDeptno(int deptno) {
this.deptno = deptno;
}
public String getName() { // name
return dname;
}
public void setDname(String dname) {
this.dname = dname;
}
public String getLoc() {
return loc;
}
public void setLoc(String loc) {
this.loc = loc;
}
}
查询到数据后，进行修改
@WebServlet(urlPatterns = "/update2")
public class Update2 extends HttpServlet {
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("utf-8");
int deptno = Integer.parseInt(req.getParameter("deptno"));
String dname = req.getParameter("dname");
String loc = req.getParameter("loc");
Connection conn = null;
PreparedStatement stmt = null;
try {
conn = Utils.getConnection();
stmt = conn.prepareStatement("update dept set dname=?, loc=? where deptno=?");
stmt.setString(1, dname);
stmt.setString(2, loc);
stmt.setInt(3, deptno);
stmt.executeUpdate();
} catch (Exception e ) {
e.printStackTrace();
} finally {
Utils.close(stmt, conn);
}
resp.sendRedirect("/select");
}
}
查询并自定义分页
@WebServlet(urlPatterns = "/select")
public class Select extends HttpServlet{
@Override
protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String page = req.getParameter("page");
String size = req.getParameter("size");
//页数
int p = 1;
if(page != null) {
p = Integer.parseInt(page);
}
//每页四条记录
int s = 4;
if(size != null) {
s = Integer.parseInt(size);
}
//m,n是限制查询的参数
int m = (p-1)*s;
int n = s;
Connection conn = null;
PreparedStatement stmt = null;
ResultSet rs = null;
try {
conn = Utils.getConnection();
stmt = conn.prepareStatement("select deptno,dname,loc from dept limit ?,?");
stmt.setInt(1, m);
stmt.setInt(2, n);
rs = stmt.executeQuery();
List list = new ArrayList<>();
while(rs.next()){
list.add(new Dept(
rs.getInt("deptno"),
rs.getString("dname"),
rs.getString("loc")
));
}
//计算总页数
stmt = conn.prepareStatement("select count(*) from dept");
rs = stmt.executeQuery();
rs.next();
int count = rs.getInt(1);
int total = 0;
if(count % s == 0) {
total = count / s;
} else {
total = count / s + 1;
}
req.setAttribute("p",p);
req.setAttribute("aaa", list);
req.setAttribute("total", total);
req.getRequestDispatcher("select.jsp").forward(req, resp);
} catch (SQLException e) {
e.printStackTrace();
} finally {
Utils.close(rs, stmt, conn);
}
}
}
三 ：以下是上面代码所需要的jsp代码
insert.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
新增部门
select.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" import="java.util.*,westos.Dept" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
Title
${d.deptno}
${d.name}
${d.loc}
删除
修改
新增
update.jsp
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
Title
要修改的用户不存在!
${d.deptno}, ${d.name}, ${d.loc}